Ballast apparatus



United States PatentA BALLAST APPARATUS Roger E. Hume, Danville, Ill., assignor to General Electric Company, a corporation of New York Filed Aug.l 17, 1959, Ser. No. 834,317

6 Claims. (Cl. 315-138) This invention relates to ballast apparatus for start-ing and operating gaseous discharge lamps such as uorescent lamps. It is concerned with ballast apparatus especially advantageous for use with the so called instant start type of lamp which requires an instantaneously high voltage sucient to initiate the gaseous discharge in the lamp without the necessity of heating the elements thereof. Once the discharge has been initiated in the lamp, it is then required of the ballast apparatus that current ow be limited for the reasons well-known and inherent to gaseous discharge lamps.

One popular form of ballast apparatus used with fluorescent lamps, and particularly with instant start lamps, is arranged for sequentially igniting and controlling the current to a pair of lampsconnected in series circuit relation with each other. Such ballasts and circuits are described, forvexample, in United States Patent 2,358,810- Karash and in United States Patent 2,558,293--Feinberg- In such apparatus, an auxiliary high reactance element provides voltage for igniting one of the lamps and the resultant current through this ignited lamp functions in conjunction with other reactance elements in the circuit to ignite the other serially connected lamp. After both lamps are started, they are then operated by the apparatus in series circuit relation withthe auxiliary high reactance element being substantially bypassed by the lamp current. For economy and simplicity, all of the desired inductive reactance elements are now general-ly provided by separate secondary windings on a unitary magnetic core structureforming a ,single high-reactance transformer in which the starting reactance or winding is arranged on one side of the primary winding and the ballasting reactance or winding is on the other side of the primary winding. This form of ballast apparatus is commonly known as a series sequence ballast. Besides this common arrangement, it has also been suggested, as for example in United States Patent 2,683,243-Feinberg, that a portion of the ballasting winding may be wound over the primary winding in additive voltage relation thereto for increasing the voltage applied to the lamps during their operation.

Diiculty has been experienced, however, in economically adapting the series sequence ballast design .to highvoltages, for example, to discharge devices ioperating fromy a 277 volt supply source. As is well-known, normal residential and commercial distribution voltage is in the .range from 110 to 240 volts; industrial voltages are generally distributed at 220 to 480 volts. ln a three phase 480, volt system, the line. to neutral of thesystem is at approximately'277 volts,.and there is presently a growing demand for lighting circuits yto operate -from 27 '7 volt circuits. f

on 'suchhigh-voltages, itis not economical to design a,

separate ballast core for the high-voltages'vballast. Presentdesign philosophy for series,y .sequenceballasts for.

starting and operating Vinstant 'st aftlamps is that the high volumeulguvolt' 60 cycle core design is the basic design. From-ari economical' standpoint;thi`s`" basic design usually has a core developed for optimum performance at the lowest possible cost at the high volume voltage. Because of low volume, ballasts for other voltages and frequencies of this type are of secondary nature in as far as expended design eort is concerned; it is, therefore, desirable that the 277 volt input ballasts be designed on the volt ballast core. However, for ballast designs using the 120 volt core, but fin the 265 and 277 volt range, dificulty is encountered in proper operation of the lamps. For example, if a A277 volt ballast were being designed on the 120 volt core punching, the primary winding could easily be changed and put in the same physical space as the 120 volt primary Winding; but, a higher voltage would appear across the starting winding and would cause higher, abnormal current in the starting winding. The increased current would make the starting winding exceed coil temperature requirements. Ballast turns could not be added to the starting winding to incre-ase the impedance due to the space limitation. In the ballasting circuit under normal conditions, the added voltage would cause poor lamp current wave form, considerable unbalance between lamps, high capacitor voltage and a hotter unit. If the higher voltage is compensated for by removing turns from the ballasting winding, this produces a greater problem of low frequency variation in light outputor instability.

Certain improved ballast apparatus described and claimed in co-pending application Serial No. 829,148,

filed on July 23, 1959v by Daniel Lovinger, asa continu as well as over the apparatus disclosed in the aforementioned Karash and Feinberg patents; and it has as its primary object the provision of animproved ballast apparatus for initiating the discharge of a pair of instant start lamps and for thereafter operating the same,l which apparatus is economically capable of being adapted to operate on high-voltage sources. l

Another object of the invention` is to provide an improved ballast apparatus which s arranged forenergization from a high-voltage source, but may use the same magnetic' core as ballast apparatus adapted for .energization from a lower voltage source.

A further object is to provide an improved ballast apparatus for use with a high voltage source, which operates at high eiliciency to start and operate a pair of instant start lamps. .f

As mentioned above, the series sequence ballasts commonly used todayhave all oftheir windings positioned on a single magnetic core. In particular, one popular ballast comprises an autotransformer havinga primary, a loosely coupled first or auxiliary starting secondary having one side connected'to one side of the primaryand in additive voltage relationship thereto, and ay loosely connected second or operating secondary more closely series with a capacitivereactor across the primary andthe lirst'jsecondary, and the second of the llamps is connected across the firstl and second secondaries in series. "In'the apparatus disclosed in the aforesaid Lovinger application Ser-ial l}Io.f-8I29,l48, 'the transformer is modified for highvoltages, in excess of the normal commercial and residential volta' jjbyf theaddition of a third secondary co' closelyy 'cbupled -to the primary coil and bucking the fcom'- 1 bined terminal volta'geof the primary` coil and lsecond.A or

operating secondary. According to the present inveptiop,

8 the third or .bucking secondary is so :arranged `and Vconnected that it opposes the voltages of the primary and the operating secondary duringthe operation of the lamps, but doesmot oppose the voltage ofthe.operating-secondary;in,the.-.starting circuits'for-the lamps. ,Therebyyan improved ballastis provided givinggoodlamp -balance .and operating atY high eciency.

The subjectmattertwhichl regard as my inventionfis particularly pointedout and` distinctly claimedin the concluding portion of-thisspecication. `My invention, however, both as.tolorganizationand method of operation, together with further objects-andadvantages thereof, may be best understoodlby reference to the'following'description taken in conjunction Iwithrthe'accompanying drawing, in-which:

Fig. l is -afschematic diagram illustrating a ballast ap- -paratus embodyingmy-invention Vconnected -to start and operate Y two gaseous discharge lamps; and,

Fig. 2 is a plan view-of the ballast apparatus included in arrangement of Fig. l.

Referring' to Figs. l andf2,the,illustrated embodiment of my invention -employs a magnetic core 1, which includes a center'winding'leg 2 and an enclosing yoke 3. Several independently formed Vwindings are wound on the center leg 2, including aprimary winding P, a first or starting secondary windingS1, a second or operating secondary winding S2, and -a third or voltage compensating secondary winding S3. The secondary windings lare in inductive relationship to the primary winding, all being wound on the commonmagnec `winding leg 2. The 'tirstlsecondary S1 andthe second-secondary S2 are both yloosely coupled lto the primary-P, 'but .the thirdsecondery S3 is closely coupledto Athe .primary "P.

1In ;the illustrated vembodimentthe ythird secondary S3 is wound directly over the primary P to provide the desired close coupling. 'With this arrangement there is, of course, substantially no fleakage reactance 'between the primary andgwinding S3. It willbe understood, however, thatin alternateembodiments of the invention the secondary S3 could be positioned immediately beside the primary `P on the winding'leg Zjinstead of being wound over the primary. With this .alternate arrangement `the winding S3 wouldl be relatively shortin length and would be quite closely coupled to `theprirnary, with relatively littleleakage flux therebetween. As in the illustrated embodiment, the winding vS3 would bermuch more closely lcoupled to the yprimary than either Yof the windings S1 and S3, whose arrangement will ,now lbe described.

shown, the rst or starting secondary S1 is positioned Vadjacent one end ofthe winding leg 2 spaced from the primary Pand with a ux leakage path or shunt 4 formed between it and the primary. The leakage path 4 is formed by oppositely disposed projections on the yoke 3 which project inwardly toward the winding leg 2, with an airgap between them and Vthe winding leg at their innerends. With this `arrangement, the starting secondary ,S1 is loosely coupled to the primary P, having a rather high leakage reactance. The other or operating s econdary S73 is Vpositioned on v,theopposite end of the ywindingrleg with ajux leakage path or shunt 5 formed between it and the primary P. Withfthis arrangement, the windingSz is also a high reactance winding, loosely coupled to the primary P, butinthe illustrated embodiment its arrangement is .such that it is more closely l coupled `to the primary than the starting .secondarySp `It will be .understoodincidentallytthat the present in- .vention isnot limitedftony particulararrangementfor `proyidin g flux :leakage 4paths Yor 4shunts Vbetween the primary? ,and `the secondaries, S1 and vS3 since depending upon `the designof `the transformer, 4,either air leakage maths vernritiectims,0.11 thecerelmay ,be-used .to provide therlesired .'.ux .leakage arrangements- Whatever Varrangement is. umd. however.. .the .Startins .Secondary Si -will'jbe'of ajjhig'her-reactance than theoperating secondafysa. i

-The windings i otthe Ytransformer 1 are connected,n the illustrated embodiment of my invention, in the circuit of Fig. l, and the relative directions of the open circuit or generated voltages therein are indicated by the arrows next to the respective windings.

in the circuit of Fig. l, the starting secondary winding S1 is connected in autotransformer relationship to the primary P at juncture 6, and is arranged so that its open circuit voltage is additive to that of the primary. The third secondary winding S3 is connected in autotransformer relation to the otherend of winding-S1 at connection point 7,but it is-arranged in.an Vopposite opencircuit electrical direction to provide open-circuit bucking or opposing voltage to -the first secondary winding S1 and primary winding P. The primary P and the secondaries S1 and S3 are all connected in series circuit relation in a loop for starting the lamp L1, as will be explained hereinafter. The operating-secondary winding S3 is also connected to'the end of the secondary S1 remote from the primary'P, and it isarranged in an opposite or bucking open-circuit electrical sense to the starting secondary winding S1 in a second series loopincluding lamp L2 but excluding the lamp L1. In this second loop-the lamp L3 is serially connected with both secondaries S1 and S2. Also, as will be further described below, secondary S3 and secondary S3 are both included in the normalfseries operating loopincluding both lamps L1 and L2, with S3 providing a-generally opposing or bucking voltage `to S31in the operating-loop.

The primary winding P-is provided with leads 8 and 9 for connection across a Asource Vof alternating current voltage, and `leads 10 Yand llfextend 'from `the -ballasting apparatus `for connection `to Va jrst `discharge lamp 1.1. The lead 10 is-connected-to one side ofthe primary uP as by input lead 8, and the lead 11 is-connected to the end of secondary S3 -remote `from connection point 7. As shown, a capacitive-reactor 12 is serially connected in thelead 11 between'winding'S3 and lamp'L1. yWhen lamp L1 is placed across the leads 10 and11, it is thereby connected in a series starting-loop comprising the primary winding P, the starting secondary winding S1, the third secondary winding S3 and "the capacitive reactor 12. Winding S3 provides a bucking voltage tothe primary P and secondary S1 in this loop, but the combined opencircuit voltage of-the primaryP vand the starting secondaryS1 is -much lgreaterthan that of s econdary'S3so that suicient voltage is'supplied to lamp L1 to start lamp'L1.

Another-set of leads13fand`14 extend from the ballasting'apparatus 'for connection tothe second lamp L3. The lead 13 is connected to the other side of the primary Yfrom lead 10, i.e., to-input lead 9, and the lead 14 is connected to `the end of the operating secondary Sz'remote from point 7. `The leads 13 ,and 14 thus connect the lamp L3 in a series loop comprising it and the secondaries S1 and S3. This loop, as will now be explained, iseffective to ignite the lamp L2 once the lamp L1 has been ignited by its starting loop. Specically after'thelamp L1 has started, current tlows in the starting loop :including lamp L1 and since the inductive reactance `of the loosely coupled vstarting secondary SV1 is ,greatcompared to the capacitive reactance of the reactor 12, `the current in the looprislagging. The lagging current ow caused bythe ignition of the rst lamp,L1 gives rise to a reactive voltage in the starting secondary S1 whosephase is in effect reversed relative to the phase of voltage 4in the primaryP Aand hence is generally additive `relative to the voltage induced in the Voperating secondary 53. This voltage s of such magnitude that ,the combined voltage` appearing across jlamp'L3 'from secondary Windings S1 and S3 is suicientfto ignite'the lampjL3. Lamps L1 and aL3are thereby started seguentially. It will be :Specially noted that winding S3 idees not supply ,any bucking Yeltaseinthe 1091 for Startnslamplg.

With bothtlarnnslqneratinathe Qperating-logp-,consists of a series circuit connected across the primary P. Starting at lead 9, this circuit comprises lead 13, the lamp L2, lead 14, the operating secondary winding S2, tlevthird secondary winding S3, the capacitive reactor 12, lead 11,- the first lamp L1, and lead back to the other input lead 8.v Because of the very high reactance of the starting secondary S1, it carries very little operating current, and `therefore, is not considered as part of the operating circuit. It will be seen that the voltages of the primary P and the operating secondary-S2 are additive in the operating loop, but that the voltage of S3 is in opposing or buckling relation in the` loop.

As heretofore explained, where the source voltage is higher than the normal 120 volt commercial and residential voltage, for example, as where the above-mentioned 277 volt high voltage is employed, the voltage in the operating circuit, without the adidtion of the bucking voltage of the third secondary S3, would exceed the normal operating voltage needed for the lamps, thereby distorting the lamp balance. The provision of the bucking voltage produced by third secondary winding S3, permits normal operation of the lamp circuit; it is not necessary to sacrifice operating secondary reactance by the removal of turns from the operating or ballasting secondary S2. The voltage of the secondary S3 reduces the toal voltage in the operating circuit to the desired assegno first secondary winding and said primary winding all lationship to both said first and second secondary windings, leads for connecting a first discharge lampin 'a starting loop including said third'secondary winding, said serially connected, and for connecting the second lamp in a starting loop including said first secondary winding and said second secondary winding, and for connecting both lamps in a series operating loop including 4said primary winding, said third secondary winding and said second secondary winding, all serially connected, said third secondary winding being in opposing voltage relation to said primary winding and said second secondary winding thereby to reduce the operating voltage applied to said lamps without substantially affecting the inductive ballasting reactance in said circuit and said first secondary winding having sufficient reactance so that said first secondary winding is substantially isolated from said operating loop when said lamps are ignited.

2. Apparatus for sequentially igniting and operating a pair of gaseous discharge lamps in a series operating circuit from a -source of high voltage supply comprising amount without reducing the inductive ballasting re- 'Y act-ance and thereby provides for eicient lamp operation.

In'a typicalembodiment of my ballastr apparatus, in-` tended for use with a voltage source of 277 volts to energize two 96T12 instant start lamps, the windings are arranged so that the open-circuit induced voltage in the starting secondary S1 is approximately 625 volts, the

open-circuit induced voltage in the operating windings; is approximately 350 volts, and the open-circuit induced1 i voltage in the third or bucking winding S11-is approx'- f35 mately 159 volts. During the steady state operation of the ballast, the lamps are in good balance with a'current of approximately 0.405 ampere fiowing in lamp L1 and approximately 0.395 ampere in lamp L1. The ballast has the very considerable advantage that it uses the same core as is normally used for the higher volume 120 volt ballasts, whereby it may be inexpensively produced without design, tooling and other expense necessary for a special core. Further, of any ballasts known to me for use with a 277 volt supply to energize two 96T12 instant start lamps, this ballast consumes the least voltamperes. Thus, from an operating or efficiency standpoint, as well as a manufacturing viewpoint, the ballast is quite desirable.

In accordance with the Patent Statutes, I have described what at present is considered to be the preferred embodiment of my invention. However, it will be obvious to those skilled in the art that various changes and modifications may be made in the disclosed structure without departing from my invention, and it is, therefore, aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. Apparatus for igniting and operating a pair of gaseous discharge lamps from a source of high voltage supply comprising a magnetic core having wound thereon a primary winding, a first high reactance secondary winding loosely coupled to said primary winding, a second high reactance secondary winding loosely coupled to said primary winding, and a third secondary .winding more closely coupled to said primary winding than either of said first or second secondary windings; means connecting said first secondary winding to said primary winding in autotransformer relationship with their open-circuit voltages in aiding relation, means connecting said third secondary winding in autotransformer relationship with both said first secondary winding and said second QQQQIIdary winding in open-circuit opposing voltage rea magnetic core having wound. thereon a primary winding, a first high reactance secondary winding, said first secondary-winding having sufficient reactance to be substantially isolated from said series operating circuit a second 'highreactance secondary winding, and a'third secondary winding placed on said primary winding and closely-coupled thereto, flux leakage paths between said primary `winding and each of said first and second secL ondary windings, said first secondary winding having one' end connected to said primary winding in autotransformer relationship with -their open-circuit voltages in aiding relation, said third secondary winding-having :one endconnected to both saidl first secondary winding and said Nsecond secondary winding and arranged in open-circuit l''oppo"sr'1'gvoltage relationship `to both said first secondary winding.-andsaidsecond-secondary winding, a capacitive reactor, leads for connecting a first discharge lamp in a starting loop including said capacitive reactor, said third secondary winding, said first secondary Winding and said primary winding all serially connected, for connecting the second lamp in a starting loop including said first secondary winding and said second secondary winding, and for connecting both lamps in a series operating loop across the capacitive reactor, the primary winding, all serially connected, said third secondary winding being in opposing voltage relation to said primary winding and said second secondary winding thereby to reduce the operating voltage applied to said lamps without substantially affecting the inductive ballasting reactance in said circuit.

3. Apparatus for igniting and operating a pair of gaseous discharge lamps from a source of high voltage supply comprising a magnetic core having wound thereon a primary winding, a first high reactance secondary winding, asecond high reactance secondary winding, and a third secondary winding closely coupled to said primary winding, flux leakage paths between said primary winding and each of said first and second secondary windings, said first secondary winding having one endconnected to said primary Winding in autotransformer relationship and having an open-circuit voltage in aiding relation therei and for connecting the second lamp in a starting loopV including said first secondary winding and said second secondary winding, said leads connecting both lamps in a series operating loop including said primary winding, said third secondary winding, and said second secondarg ansiado ing beingin opposing voltage relationfvto said primary winding-and said -secondtsecondary windingand said first secondary .winding having sufficientE reactance yso that said rst winding `is substantially isolatedfrom ysaid series operating loop.

44. Ballast apparatus ,for sequentially starting .and'operating a pair of gaseous dischargelamps ina seriesoperating circuit from an alternating'current i source, comprising va multiple winding `transformer ,having a primary winding for connection to said* alternating current source, a 'ballasting secondary -winding loosely coupled to said primary'winding, a starting secondary `winding loosely coupled to `said primary winding :and having suicient reactance to belsubstantially isolated from 4,said series operatingcircuit,anda third secondary windingrclosely coupled to said primary winding, means for-,connecting a part of said transformer including at least said starting secondary winding for applying igniting Vvoltage to onevof said lamps, means for connecting a part of said transformer including saidstarting and ballasting windings Vand excluding said `third winding for applying igniting voltage to the other of said lamps, said ballasting winding and said third winding being serially interconnected for connection with both of said lamps across said ,primary to formsaid series operating circuit for saidlamps, said third winding being connected :in voltage bucking .relation `torsaid ballasting winding in -said operating circuit thereby to reduce .the operating voltage applied .to

said lamps.

5. .Ballast ,apparatus `for :sequentially igniting :and .zop-

-erating a pair of fluorescent lampsin a'series operating circuit from :a relatively .high voltage alternating "current ber, a high reactance starting secondary winding .having 'su'icientireactancesdthat said starting winding is sunstantially isolated from the operatingl circuit, a hightre- Vactance .ballasting secondary winding, a primary winding anda third secondaryiwinding all located onsaid winding leg, 4with .said -third .secondary winding being closely coupledto .sai-d primary, a capacitive reactor 4connected in series circuit relation with `said ballasting winding and said `third secondary winding for interconnection with both ofsaid lamps across/.said primary, said third -winding being connected in voltage bucking relation to saidvballasting winding in the series'connection with said capacitive reactor, said starting winding, said primary winding, and said third winding forming a series operating loop for starting onefof said lamps whereby said voltage across said third -windinglisiin an aiding relation with the voltage across said primary winding and said starting winding being connected from one side of lsaidprimary winding tothe juncture between said ballasting winding andsaid third winding whereby said voltage across said third secondary 'winding is ;in an opposing relation to the voltage acrosssaid `ballasting secondary Awinding during operation'ofsaid. lamps.

6. .The apparatus of claim 5 whereinfsaid-third winding is wound overisaid yprimary winding, said ballasting winding yand said starting winding are disposed on opposite sides Vof said primary `winding .and ux leakage .pathsare provided betweensaid primary winding'and said ballasting and` startingfwindings.

References Citedin the le of this pateht LUNTI'ED 'STATES IPATENTS 25558293 'Feinberg 1111152651951 '26481802 Kazebee Aug, 11,1953 '27883169 Fitiberg Apr. 9, `14957 "2,789,252 TenDam Apr. 16, 1957 Patent NMu i2,965,800 December 2.o 1960 Roger Eo Hume It is hereby certified/that error ent requiring correction and that the s corrected below.

appear-s in the above numbered pataid Letters Patent should read as Column s,

line l5, for "aiding relation" read bucking relation u.

Signed and sealed this 18th day of July 196i.

(SEAL) Attest:

ERNEST W. SWIDER Attesting Officer DAVID L. LADD Commissioner of Patents 

